1. Technical Field
The present invention relates to a physical quantity detector (pressure sensor).
2. Related Art
As a physical quantity detector (pressure sensor) such as a water pressure gauge, a barometer, and a differential pressure gauge, the detector including a diaphragm that is deformed in response to received pressure and a piezoelectric vibrator that is subjected to stress with the deformation of the diaphragm, and detecting pressure based on the resonance frequency of the piezoelectric vibrator has been known (for example, see Patent Document 1 (JP-A-2010-48798)).
For example, in the pressure sensor disclosed in Patent Document 1, the diaphragm includes a flexible region having flexibility provided between a center region and an outer circumferential edge region, and the center region (displacement part) is displaced in response to the pressure in the thickness direction. Further, the piezoelectric vibrator has a pair of base parts and a vibrating part provided between the pair of base parts. Further, the pair of base parts are provided in line in the direction in which the diaphragm deflects, and one base part is connected to the center region of the diaphragm and the other base part is connected to the outer circumferential region of the diaphragm via a columnar support member.
In the pressure sensor disclosed in Patent Document 1, the support member is formed integrally with the piezoelectric vibrator. The support member and the piezoelectric vibrator are formed using the same material, and thereby, the error of the detected pressure due to the difference in coefficient of linear expansion between the support member and the piezoelectric vibrator (the error due to thermal strain) may be reduced.
However, in the pressure sensor disclosed in Patent Document 1, the support member is connected to the diaphragm, and there is a problem that unintended displacement and deformation of the support member are produced with the deformation of the diaphragm and, as a result, reduction in detection accuracy is caused.
If high stiffness is provided to the outer circumferential edge region of the diaphragm, the length of the support member in the direction orthogonal to the direction in which the diaphragm deflects becomes longer and unintended displacement and deformation of the support member may be easily produced and the reduction in detection accuracy may be caused.